The present invention relates to a television synchronizing signal generating apparatus and, more particularly, to a PAL system synchronizing signal generating apparatus which outputs synchronizing signals such as a subcarrier, a horizontal driving synchronizing (H sync) signal, a vertical driving synchronizing (V sync) signal, a composite synchronizing signal, a composite blanking signal, a burst flag signal and a PAL identification signal.
In a PAL system, the relationship between the color subcarrier frequency f.sub.sc and the H sync signal frequency f.sub.H is given by ##EQU1## Because of the offset term (1/625)f.sub.H in the equation (1), it is impossible to produce the H sync signal by simply multiplying and counting down the subcarrier frequency f.sub.sc. Accordingly, the other synchronizing signals, that is, the V sync signal, the burst flag signal, the PAL identification signal and the blanking signal which rely upon the H sync signal, are difficult to produce.
An integrated circuit capable of producing the H sync signal, V sync signal etc. has been developed and offered on the market. This integrated circuit (IC) requires a clock signal having a frequency n-times as large as the H sync frequency. One example of such an integrated circuit is HD 44007 produced by Hitachi Ltd. in Japan which requires a frequency 282 times that of the H sync frequency as the clock signal. Therefore, a prior art
system synchronizing signal generator contains two oscillators, i.e., an oscillator for producing a subcarrier and an oscillator for producing the clock of a frequency n-times higher than the H sync signal frequency, and requires a very complicated circuit.